Sciatic pain can also be a sign of dehydration

If you are dong the Master-Cleanse with two coffee enemas, you may be really stressing your kidneys - make sure you guzzle tons of water. And stretching the kidney/bladder meridian or having it massaged may help, too.. it runs down the back of your legs.
The Liver Flush can dehydrate you, too. And making sure to get enough of the syrup is a very good idea.
I personally would let up on the coffee enemas until after the MC... the Master-Cleanse is a powerful liver cleanser, too. I did it to begin with to cleanse the liver/gall bladder in prep for a flush - after a gall stone attack.
Best,
LN